Bryan Kohberger fancied himself a criminal mastermind — so why’d he make so many dumb mistakes?

Well, that’s one way to fail criminology school. 

Bryan Kohberger had been in a PhD in criminology program at Washington State University when he drove to the nearby Moscow, Idaho, and slaughtered four University of Idaho undergrads in 2022.

But for that crime, this student gets an “F.” 

It wasn’t that he didn’t try to cover his tracks: Kohberger clearly had a firm grasp of common investigative techniques and took pains to subvert them — including scrubbing his car meticulously clean after the killings.

But his attempts were so half-baked that they only made him seem more suspicious, according to prosecutors.

Experts say he attempted to cover his tracks, and was more careful than killers — but he made some obvious mistakes.

“He was certainly smarter than most murderers,” a former federal prosecutor Neama Rahmani told The Post. “But it wasn’t the perfect crime.”

Rahmani noted that it took weeks for authorities to find the suspect, which is “atypical now with advances in technology.”

These are some of Kohberger’s biggest blunders.

Leaving his DNA behind

The murder weapon was never found, but a knife sheath smudged with male DNA left at the scene became the prosecution’s best piece of physical evidence.

Rahmani said the blunder revealed that the the killings were harder than Kohberger expected — betraying a “a chaotic scene when you’re stabbing multiple people and you’re just by yourself.”

“It’s not easy,” he added.

Another former prosecutor and Court TV anchor Vinnie Politan said Kohberger likely “ran into an unexpected situation,” when one of the victims, Madison Mogen, wasn’t alone. She and best friend Kaylee Goncalves were sleeping together in the same bed.

They were the first victims.

And the dropped sheath likely revealed that they did not die without a struggle.

“The women fought back, and in the struggle” the knife sheath fell out, Politan speculated.

“Then when he was leaving he ran into Xana [Kernodle] then Ethan [Chapin], two more unexpected victims,” Politan explained. “He was exhausted and didn’t have time to think, so he left without any realizing he didn’t have the sheath.”

Buying the murder weapon on Amazon

Prosecutors said Kohberger purchased a KA-BAR military-style knife, a strap sheath, and a sharpener on Amazon while living at his parents’ house in Pennsylvania months before the murders.

He seemed to know his online purchases might be traced: He used a gift card, which can be anonymous, to make the payments and even tried to delete his purchase history.

But why make the purchase online at all when anyone can buy a knife with cash at any Walmart or truck stop?

Defense attorney David Seltzer said, “clearly Kohberger left break crumbs linking him to the crimes, and we will never know why, or if they were heat-of-the-moment mistakes.”

Seltzer said he wouldn’t be surprised if mental health played a role in Kohberger’s crimes.

Driving his own car to the crime scene, then cleaning it too well

Kohberger’s white Hyundai Elantra is what first landed him on detectives’ radar.

Security camera footage showed the car circling the victims’ block, parking behind their house, and then speeding away after the crime.

A search of white Elantra drivers included Kohberger, who had been pulled over near the University of Idaho campus months before the killings.

He did thoroughly clean the interior of the car afterward, prosecutors said – but that only made him seem more suspicious, Latah County Prosecuting Attorney Bill Thompson revealed Wednesday.

“I think we can all look to our own cars. Those compartments in the doors where you try to keep them clean where you put stuff? There’s always some degree of crud in there — they were spotless,” Thompson said. “Defendant’s car had been meticulously cleaned inside.”

Thompson noted that Kohberger has previously written a paper on crime scene evidence collection — making his deep-clean even more suspicious.

His phone also tracked him driving to Moscow, Idaho — the town where the killings happened — at least 23 times before the murders.

He kept his own phone

Anyone who’s watched “Breaking Bad” knows to use a prepaid, burner cell phone when they’re up to no good.

But Kohberger kept a traceable cell phone.

He was careful to deactivate the device before driving to Moscow on the night of the murders, but it was only off between around 2:30 a.m. and 4:45 a.m. – the exact window of the killings.

He also reactivated the phone in another town 25 miles away from his apartment.

Rahmani said Kohberger should have just left his phone at home.

“He was careful,” the lawyer said. “But he’s not a genius.”

Taking out the trash

Kohberger knew that his DNA could tie him to the crime scene: He wore latex gloves to the supermarket and hid trash that contained his hair or saliva.

At one point during the four days he was surveilled at his parents’ Pennsylvania home by the FBI prior to his arrest, Kohberger was observed putting trash from his family’s house into neighbors’ garbage bins around 4 a.m.

Kohberger clearly knew investigators search suspects’ garbage, but it apparently didn’t occur to him that agents might be watching the house — nor catch him dumping garbage in the small hours.